全文获取类型
收费全文 | 688篇 |
免费 | 31篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 43篇 |
综合类 | 8篇 |
化学工业 | 269篇 |
金属工艺 | 20篇 |
机械仪表 | 12篇 |
建筑科学 | 23篇 |
矿业工程 | 1篇 |
能源动力 | 42篇 |
轻工业 | 70篇 |
水利工程 | 1篇 |
无线电 | 36篇 |
一般工业技术 | 116篇 |
冶金工业 | 28篇 |
原子能技术 | 14篇 |
自动化技术 | 41篇 |
出版年
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 18篇 |
2020年 | 4篇 |
2019年 | 16篇 |
2018年 | 10篇 |
2017年 | 19篇 |
2016年 | 16篇 |
2015年 | 13篇 |
2014年 | 23篇 |
2013年 | 44篇 |
2012年 | 26篇 |
2011年 | 39篇 |
2010年 | 29篇 |
2009年 | 33篇 |
2008年 | 50篇 |
2007年 | 32篇 |
2006年 | 28篇 |
2005年 | 27篇 |
2004年 | 20篇 |
2003年 | 25篇 |
2002年 | 28篇 |
2001年 | 18篇 |
2000年 | 21篇 |
1999年 | 10篇 |
1998年 | 25篇 |
1997年 | 18篇 |
1996年 | 19篇 |
1995年 | 11篇 |
1994年 | 7篇 |
1993年 | 11篇 |
1992年 | 8篇 |
1991年 | 9篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1986年 | 3篇 |
1984年 | 3篇 |
1983年 | 7篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1969年 | 1篇 |
排序方式: 共有724条查询结果,搜索用时 31 毫秒
711.
D.A.L. Lourenco I. Misztal S. Tsuruta I. Aguilar T.J. Lawlor S. Forni J.I. Weller 《Journal of dairy science》2014
Data sets of US Holsteins, Israeli Holsteins, and pigs from PIC (a Genus company, Hendersonville, TN) were used to evaluate the effect of different numbers of generations on ability to predict genomic breeding values of young genotyped animals. The influence of including only 2 generations of ancestors (A2) or all ancestors (Af) was also investigated. A total of 34,506 US Holsteins, 1,305 Israeli Holsteins, and 5,236 pigs were genotyped. The evaluations were computed by traditional BLUP and single-step genomic BLUP, and computing performance was assessed for the latter method. For the 2 Holstein data sets, coefficients of determination (R2) and regression (δ) of deregressed evaluations from a full data set with records up to 2011 on estimated breeding values and genomic estimated breeding values from the truncated data sets were computed. The thresholds for data deletion were set by intervals of 5 yr, based on the average generation interval in dairy cattle. For the PIC data set, correlations between corrected phenotypes and estimated or genomic estimated breeding values were used to evaluate predictive ability on young animals born in 2010 and 2011. The reduced data set contained data up to 2009, and the thresholds were set based on an average generation interval of 3 yr. The number of generations that could be deleted without a reduction in accuracy depended on data structure and trait. For US Holsteins, removing 3 and 4 generations of data did not reduce accuracy of evaluations for final score in Af and A2 scenarios, respectively. For Israeli Holsteins, the accuracies for milk, fat, and protein yields were the highest when only phenotypes recorded in 2000 and later were included and full pedigrees were applied. Of the 135 Israeli bulls with genotypes (validation set) and daughter records only in the complete data set, 38 and 97 were sons of Israeli and foreign bulls, respectively. Although more phenotypic data increased the prediction accuracy for sons of Israeli bulls, the reverse was true for sons of foreign bulls. Also, more phenotypic data caused large inflation of genomic estimated breeding values for sons of foreign bulls, whereas the opposite was true with the deletion of all but the most recent phenotypic data. Results for protein and fat percentage were different from those for milk, fat, and protein yields; however, relatively, the changes in coefficients of determination and regression were smaller for percentage traits. For PIC data set, removing data from up to 5 generations did not erode predictive ability for genotyped animals for the 2 reproductive traits used in validation. Given the data used in this study, truncating old data reduces computation requirements but does not decrease the accuracy. For small populations that include local and imported animals, truncation may be beneficial for one group of animals and detrimental to another group. 相似文献
712.
The scaling dependence of electron transport in the double-gated Schottky barrier MOSFET (DG-SBT) below 10 nm is investigated
in the framework of quantum transport theory, using non-equilibrium Green’s function method. Simulation results show that
the current-voltage characteristics in ultra-small DG-SBT are characterized by both resonant and direct tunneling effects.
The electron potential in the 10-nm-scale DG-SBT surrounded by Schottky barriers acts as a resonant cavity and produce a negative
differential resistance due to resonant tunneling effect. While, further scaling shallows the depth of the cavity and makes
it difficult to form resonance levels. Hence, at the scaling limit, direct tunneling currents simply dominate the current-voltage
characteristics of DG-SBT. 相似文献
713.
In reforming of CH4 with CO2 over molybdenum carbide catalysts, the catalytic performance of unsupported hexagonal Mo2C prepared by direct carburization of MoO3 was considerably different from a similar composition, cubic MoC1−x (x≈0.5), prepared through nitriding before carburization. The conversion levels over MoC1−x were substantially higher than those over Mo2C, although the turnover frequencies were lower. X‐ray diffraction analysis indicated that Mo2C deactivated by conversion to MoO2 during the reaction, but the MoC1−x was transformed to the hexagonal Mo2C and remained stable. The activity of Mo2C dispersed on various supports for the CH4–CO2 reaction was also investigated. The performance depended strongly on the property of supports, with the ZrO2‐supported Mo2C catalyst exhibiting the highest activity and durability for this reaction. Moreover, deactivation of Mo2C/ZrO2 at ambient pressure was suppressed by decreasing the loading amount of Mo2C.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
714.
Shuichi Tanoue Toshihisa Kajiwara Kazumori Funatsu Kousuke Terada Masashi Yamabe 《Polymer Engineering and Science》1996,36(15):2008-2017
In our previous study, we calculated the time course of parison length in the parison formation stage, but it could predict only the parison area swell. The next target in our study is to calculate the parison diameter and thickness swell. Annular extrudate swell simulation is necessary for the understanding of various kinds of swelling ratios in blow molding. We have examined three kinds of swells (outer diameter, thickness, and area swells) obtained from simulation results of annular extrudate swell, using the Giesekus model, and have developed a method of predicting parison outer diameter and thickness swell values. The predicted values of parison outer diameters are discussed in comparison with experimental data, and reasonable results are obtained by the proposed method. This prediction method could also be applied to the parison formation process using a parison controller. As a result, it is possible to predict approximately the whole process of parison formation by numerical simulation. 相似文献
715.
If a bacterium has motility, it will use the ability to survive and thrive. For many pathogenic species, their motilities are a crucial virulence factor. The form of motility varies among the species. Some use flagella for swimming in liquid, and others use the cell-surface machinery to move over solid surfaces. Spirochetes are distinguished from other bacterial species by their helical or flat wave morphology and periplasmic flagella (PFs). It is believed that the rotation of PFs beneath the outer membrane causes transformation or rolling of the cell body, propelling the spirochetes. Interestingly, some spirochetal species exhibit motility both in liquid and over surfaces, but it is not fully unveiled how the spirochete pathogenicity involves such amphibious motility. This review focuses on the causative agent of zoonosis leptospirosis and discusses the significance of their motility in liquid and on surfaces, called crawling, as a virulence factor. 相似文献
716.
717.
Shuichi Tanoue Toshihisa Kajiwara Yoshiyuki Iemoto Kazumori Funatsu 《Polymer Engineering and Science》1998,38(3):409-419
Annular extrudate swell simulations at high Weissenberg numbers were made using a differential type constitutive equation. The streamline-upwinding method with a sub-element for extra stress components, which is called SU4 × 4, is one of the best mixed finite element methods for computation of viscoelastic flows. Planar and capillary extrudate swell calculations at high Weissenberg numbers (We > 1000) were accomplished by SU4 × 4. However, annular extrudate swell simulations at high We by SU4 × 4 were not successful. The calculated We was less than about 4. A new calculation technique using a Newton-Raphson discretization of the equation of motion was developed. This technique is called a “new under-relaxation method.” The calculated We of annular extrudate swell simulation by the new under-relaxation method with SU4 × 4 was about 6~250 times larger than those by SU4 × 4. Reasonable calculation results were obtained in an annular flow and a capillary extrudate swell by this method, and the reliability and the utility of the new under-relaxation method are shown. It is now possible to consider the swell shapes of annular extrudate under industrially useful conditions. The calculated swelling ratios were also compared with experimental ones. 相似文献
718.
Subyakto Takeshi Kajimoto Toshimitsu Hata Shigehisa Ishihara Shuichi Kawai Hideo Getto 《火与材料》1998,22(5):207-212
Fire retardant fast-growing wood product was developed by coating with fire retardant and densifying the surface of wood. Trimethylol melamineformaldehyde resin mixed with phosphoric acid was coated on the wood surface, preheated and followed by hot pressing. Effects of the amount of coating, preheating temperature, and densifying ratio on the fire retardancy of sugi (Cryptomeria japonica D. Don) wood, and pressing temperature and pressing time on that of albizia (Paraserianthes falcataria Becker) wood were discussed. Bending strength, creep performance under fire and fire retardancy were evaluated. The results showed that the treatments improved the fire retardancy of woods without reduction in the bending strength. © 1998 John Wiley & Sons, Ltd. 相似文献
719.
Hakobu Bazaki Shuichi Kawabe Hiroshi Miya Tamotsu Kodama 《Propellants, Explosives, Pyrotechnics》1998,23(6):333-336
Hexanitrohexaaza-isowurtzitane(AC-HNIW) was synthesized by using a precursor invented by Asahi. The purity, which was measured by high performance liquid chromatography(HPLC), was determined to be 99.2%. From the results, it is expected that the propellants or explosives composed of AC-HNIW indicated higher performance in specific impulse, ballistics and detonation velocity. The structure of AC-HNIW was identified by IR and NMR. The results indicated that AC-HNIW had the same structure as CL-20 which was produced by Thiokol corporation. The sensitivity and thermal decomposition properties of AC-HNIW were also measured in order to elucidate HNIW performance. The results were compared with CL-20. The sensitivity of AC-HNIW was determined to be the same as CL-20. 相似文献
720.
In an internally circulating fluidized-bed (ICFE) boiler, the fluidized bed is separated by a partition into main combustion and heat recovery chambers. The flows in these chambers are generated by using silica sand as the fluidizing medium. To determine the overall heat transfer coefficient (HTC) of the boiler's panel-type immersed heat transfer tubes, combustion tests were performed with wire-rim tires. The overall (HTC) of a panel tube array was lower than that of a zigzag tube arrangement. In practice, the heat absorbed by the fins makes the coefficients of either type of tube array almost identical. The air flowrate in the circulating bed at the bottom of the heat recovery chamber can be changed to control the overall HTC to a value virtually identical with that of a zigzag tube array. The combustion of wire-rim tires leads to a buildup of wires in the zigzag array, hampering the transfer of heat. Yet, the panel-type array showed no buildup so that it was possible to maintain steady operation with this type of tube arrangement. © 1997 Scripta Technica. Inc. Heat Trans Jpn Res. 25 (2): 120–134, 1996 相似文献